Monday, January 26, 2015

Microscope eyepiece reticles are small circular disks that have a ruler, grid or some other measuring format printed on them that can be inserted into a microscope eyepiece. When you look through the eyepiece once the reticle is installed, the ruler or grid is imposed upon your microscopy image.

How to determine if your eyepiece accepts a reticle:

Bottom of the eyepice.

Not all microscope eyepieces are fitted to accept a reticle. In order to figure out if yours does, follow these instructions.

Remove your eyepiece from the microscope and look into the bottom of it. If your eyepiece accepts a measuring reticle, you will see a retaining ring that can be removed.

How to measure the correct diameter of reticle required:

Reticle Retaining Ring

If you see a retaining ring, go ahead and remove the ring. You will then want to measure (in mm) the diameter of the glass reticle that the eyepiece will hold. This is an important measurement as many eyepiece reticles are custom printed and can not be returned. Keep in mind that if you measure the retaining ring diameter, this may be 1mm larger than the size reticle requierd, as the glass reticle must be able to drop onto the shelf in the eyepiece, while the retaining ring will simply hold it in place. Microscope eyepiece reticle sizes are anywhere from 16mm - 28mm in diameter.

How to determine what type of microscope reticle to purchase:

Microscope Reticle

Once you know that your microscope eyepiece can accept a reticle, now it is time to determine what type will best suit your needs. The most common types of reticles are ruler reticles, crossline reticles and grid reticles. For basic measurement a ruler reticle will work well.

Determine if you would like to measure in mm or inches. Also, keep in mind that when using a ruler reticle, the distance that is between the lines when looking through the microscope follows this formula:

Reticle Division ÷ Objective Lens Value = Distance Between Lines

The magnification of the eyepiece itself has no affect on the reticle divisions you will view. For example, if your ruler reticle is 10mm with 100 divisions, your reticle division is 10 ÷ 100 = 0.1mm.

When using the 4x objective to make measurements with the above mentioned reticle, your distance between lines when measuring is: 0.1mm ÷ 4 = 0.025mm.

When using that same reticle with the 100x objective lens the distance between lines is 0.1mm ÷ 100 = 0.001mm.

Monday, January 12, 2015

A compound microscope is another name for a high power or biological microscope. A compound microscope will typically have magnifications of 40x, 100x, 400x and sometimes 1000x. A microscope advertising magnification above 1000x is simply providing empty magnification, and images above 1000x will not be clear. Blood cells, protozoans and bacteria can all be viewed at 400x magnification and it is a common misconception that more magnification is better.

Compound Microscope High Power Objective Lenses

Students typically use either a compound microscope in biology class, or a stereo dissecting microscope. A stereo dissecting microscope provides lower magnification (typically 10x - 40x) and is used to view anything you might hold in the palm of your hand such as coins, flowers, insects, or a frog. A compound microscope requires the use of slides and cover slips for viewing samples the naked eye can not see such as bacteria or cells.

A fun student science project will allow you to make your own sugar sticks (and look at sugar crystals under the microscope!)

Photo: Deisy Mejía

You will need these supplies:

Wooden skewer

Clothes pin

Tall glass

3 cups of sugar

1 cup of water

Measure the wooden skewer so that when you hold it straight down into the glass it does not quite touch the bottom of the glass. You will use the clothespin to secure it across the top of the glass. Set the clothespin and skewer aside.

Find an adult to help you boil your water and add about 1/4 cup of the sugar, stirring as it dissolves. Each time the sugar dissolves, slowly add more. Continue stirring. Each time you add more sugar it will take longer and longer for it to dissolve. Keep stirring! Once no more sugar will dissolve, turn the heat off and let it cool for about 20 minutes.

Have the adult pour the hot liquid into the tall glass. Now insert the skewer into the middle of the glass and secure it at the top with the clothespin, so it hangs straight down. Over the next week sugar crystals will form on your skewer!

If you want to make colored sugar swizzle sticks, add a few drops of food coloring to your mixture. Once you are finished making your swizzle stick, break off a small piece of rock sugar and look at it under the microscope. What do your crystals look like? If you capture some good photos email us and we will share them on our Facebook page!